The present invention relates to the construction of draw frames for thread-spinning machines and in particular to apparatus for facilitating the mounting of the roller support arm and bearing rail for the associated roving blocking mechanisms.
The conventional spinning machine is provided with a draw frame having at least a set of inlet rollers for receiving the roving from a source at least one intermediate set of rollers, and a set of exit rollers spaced therefrom between which the roving is drawn. The exit rollers feed the drawn material as threaded yarn onto a bobbin or cop on which it is wound. The sets of rollers each comprise a driven lower roller and a pair of axially spaced twin upper rollers permitting the drawing of two rovings side by side. The upper rollers are journalled in rank pairs on a common supporting load arm extending in the direction of drawing. Such machine is disclosed in the DE-OS No. 2,257,323 corresponding to Ford, U.S. Pat. No. 3,726,072 dated Apr. 3, 1973 which also provides means for sensing the proper winding of the drawn thread.
In the commonly owned copending application Ser. No. 335,210 filed Dec. 28, 1981, 4,484,376, 27 Nov. 1984, we have drsclosed several safety features, one of which comprises a device for blocking the roving at the upstream rollers when the thread or yarn breaks or ruptures at the downstream end. A holding device is also disclosed in association with the blocking device located between the upstream and the downstream rollers. This holding device provides a laterally cantilevered table which grasps the forward most end of the roving, and/or partially finished thread, so as to facilitate the manual loading of the roving preparatory to initially starting or restarting the draw frame. That is, when the operation of the drawing frame is to be initiated either initially or after a clearance of a break in a thread, the roving must be placed into the drawing frame between the upper and lower rollers. In this instance, the upper rollers are raised to permit the roving to be manually inserted between the rollers from the open side. Under normal conditions this requires special attention and manual operation on the part of the machine operator. The holder disclosed on our earlier application merely allows the forward end of the roving to be accessible for handling.
The blocking member and its switching mechanism are arranged on a bearing rail running parallel to the roving. Two bearing rails are provided for each draw frame, one on each side of the support arm holding the twin upper rollers. The bearing rails are swivelable about an axis and is provided with spring means and a stop device. The spring means holds the bearing rail in its operation position, which is horizontal and parallel to the load arm and which is determined by a stop member. The bearing rail is swivelable opposite to the spring force into a non operating position also determined by an upper stop device. A coupling yoke is mounted on the support arm. The yoke reaches over the bearing rail by means of an arm which is offset laterally at an angle and which is provided with a claw embracing the bearing rail. The claw has a degree of clearance with respect to the bearing rail which in the operating position is provided for the purpose for preventing undue force from acting on the support arm. The clearance is also important when the swivel axes of the bearing rails do not run coaxially but are offset laterally in relation to the swivel axis of the support arm. The displacement of the two bearing rails, occurring during the swiveling motion of the support arm, may then take place unhindered since the bearing rails are capable of sliding within the coupling claws of the yoke.
On the whole, this swivel bearing with its devices for determining the two swivel positions of the bearing rails and also the coupling devices with the support arm are relatively expensive. There are also difficulties in manipulating the support arm and bearing rails when the roving to be drawn is to placed on the lower rollers, with the swiveled support arm in its non operating upward position because of the coupling yoke projecting into the path of insertion.
It is the objective of the present invention to simplify the construction of the draw frame and to avoid the disadvantages and difficulties found in the prior art.
It is an object of the present invention to simplify the mounting of the bearing rail so that they pivot and are retained in both the upper and non operating position and lowered operating position in a safe operating condition.
Further advantages and objects of the present invention are set forth in the following disclosure.